Analysis of genomic imprinting of insulin-like growth factor 2 in colorectal cancer

Genomic imprinting of insulin-like growth factor 2 (IGF2) has been shown to play an important role in the development of Wilms' tumor and adult cancer s including lung and esophageal cancer. Although IGF2 has been reported to be overexpressed in colorectal cancer, the status of this gene has not been fully elucidated. To clarify genomic imprinting of IGF2 in colorectal canc er, we examined loss of imprinting (LOI) and loss of heterozygosity (LOH) i n surgically resected tissues by utilizing Apa1 polymorphism. Of 46 patient s with colorectal cancer, 2 exhibited (2/15, 13%) LOH among 15 patients who were heterozygous for IGF2 DNA in nontumorous tissues, Four (4/12, 33%) pa tients showed LOI of IGF2 gene among informative patients. in these patient s, the reverse transcription polymerase chain reaction and immunohistochemi stry revealed that IGF2 mRNA is overexpressed in tumorous tissues, compared to nontumorous tissues. Of 15 patients in whom IGF2 was immunohistochemica lly more highly expressed in tumorous than in normal tissues, there were 2 with LOH and 4 with LOI. The results of the present study suggest that LOI of IGF2 plays an important role in the carcinogenesis of colorectal cancer. Copyright (C) 2000 S. Karger AG, Basel.